1. Field of the Invention
This invention relates to novel intermediate temperature fuel cell electrolytes, fuel cells containing these electrolytes and a process for operating these fuel cells. More particularly, the invention relates to electrolyte compositions containing one or more phosphonic acids and the use thereof in fuel cells.
2. Related Art
Fuel cells are well known electrochemical devices for converting chemical energy directly into electrical energy without the intermediate thermal energy stage typical in the conventional power plant method of generating electricity. In a fuel cell, a gaseous fuel is oxidized by an oxygen containing gas to produce electricity directly. The typical cell has two electrodes immersed into and separated by an electrolyte. These electrodes are externally connected to an electrical load, e.g., an electric motor.
Fuel cells have been broadly classified into three general types. The first type is the high temperature fuel cell which operates at temperatures of greater than about 600.degree. C. The second type is the low temperature fuel cell which operates at temperatures of less than about 100.degree. C. The third type is the intermediate temperature fuel cell which operates at temperatures of between about 100.degree. C. and 300.degree. C. This invention relates to these intermediate temperature fuel cells.
These intermediate temperature fuel cells usually contain fluid aqueous electrolytes, e.g., phosphoric acid. However, these fluid electrolytes are prone to cause electrode flooding when porous electrodes are used, and further, the use of high pressures, e.g., of the order of 600 lbs. per square inch (0.4218 Kg/sq. mm) are required to prevent the water in the aqueous electrolyte from evaporating. Electrolytes that provide acceptable conductivity and yet do not volatilize readily from the fuel cell would be advantageous.
U.S. Pat. No. 3,375,138 (W.B. Mather, Jr., Mar. 26, 1968) discloses a borophosphoric acid-phosphoric acid gelled electrolyte for use in an intermediate temperature fuel cell. This patent further discloses a method for preparing this particular electrolyte gel, however, this patent does not disclose or teach electrolyte compositions as disclosed by the present invention.
Electrolytes of acceptable conductivity which do not readily volatilize would be advantageous. Fuel cells containing such electrolytes and a process for operating such fuel cells would also be advantageous.
Other objects and advantages of the present invention are shown throughout this specification.